Machine for processing plastic materials

ABSTRACT

A machine for processing plastic materials, particularly polyvinyl chloride comprising a first pair of rotating rolls, means cooperating with one of said rolls to separate the plastic material film adhering thereto, a conveyor belt receiving at least part of the plastic material, and a second pair of rolls receiving at an end zone thereof the material carried by the conveyor belt.

llmte States Patent 1191 1111 3,761,217 Mambretti Sept. 25, 1973 [54]MACHINE FOR PROCESSING PLASTIC 2,958,094 1 1/1960 Curletti 425/363 XMATERIALS 1,469,658 10/1923 McCrohan.... 425/367 x 2,788,752 4/1957Rhodes 1 425/363 X [76] Inventor: Giancarlo Mambretti, Carnago,1,503,665 8/1924 Roberts 156/231 ltaly 21040 3,674,389 7/1972 Sturgeonet al 425/224 X 22 Filed: Jan. 28, 1972 Primary ExammerRobert L. Sp1cer,Jr. 1 1 pp 221,593 AttorneyRichard P. Alberi [30] Foreign Applicationlriority Data 57] ABSTRACT 5:: 1:? A machine for processing plasticmaterials, particularly y polyvinyl chloride comprising a first pair ofrotating rolls, means cooperating with one of said rolls to sepak g giirate the plastic material film adhering thereto, a con- 58] Fie'ld 5/224363 veyor belt receiving at least part of the plastic material, and asecond pair of rolls receiving at an end zone [56] References Citedthereof the material carried by the conveyor belt.

UNITED STATES PATENTS 7 Claims, 5 Drawing Figures 1,882,160 10/1932Paris 425/363 X PATENIEB SEPZ 5 I975 SHEET 1 BF 5 MACHINE FOR PROCESSINGPLASTIC MATERIALS This invention relates to a machine for processingsuch thermoplastic materials as polyvinyl chloride (hereinafter referredto as PVC), and in the case other materials.

Particularly referring to PVC processing, it is well known that thestarting raw material may assume several forms, such as l dry mixture ofPVC powder with plasticizers, stabilizers, fillers, dyes and the like;(2) punching off-cuts and scraps as provided when manufacturingdifferent PVC sheet products; (3) thermoplastic material plates orblocks as provided by heat mixing off-cuts and scraps; and (achines)granules as provided for example by plastic material drawing andgranulating.

It is known that PVC can be converted to a continuous sheet by suchoperating machines as calenders and drawing machines. For a correctoperation, these ma-.

chines, and particularly the calenders, should be uniformy supplied witha PVC strip or card at a plastic condition. In the present art,the'common practice to supply calenders or drawing is to use acombination of a plurality of series operating machines, such machinesbeing referred to as: two-cylinder mixers, Banbury type of mixers,continuous mixers, single-or multi-screw drawing machinesQetc.

The main object of the present invention is to provide a compactversatile machine for forming a continuous hot strip directlyutili'zable by drawing machines or calenders from heterogeneous forms ofthermoplastic material, and particularly PVC.

A machine according to the invention is characterized by comprising twopairs of rolls arranged above each other, wherein one roll of at leastone pair of rolls rotates at a different speed than the other roll ofthe same pair of rolls, and in that means cooperates with one roll ofthe top pair of rolls to separate the plastic material film beingformed, film which is then brought to a conveyor means which carries theseparated material to and end of the bottom pair, where the material isprocessed to a layeradhering :to one of said rolls and tending to theother end, at which the material strip is removed by per se knowncutting means. I

The following are the major advantages of the cmpact versatile machineaccording tothe invention over any other known combination of machines:a

1. lower costof the machine with respect to a combination of machines; V

2. reduction in labour (one or more operators);

3. reduction in operating room (more than 100 percent); and a v 4.saving in electric power (in some cases more than 100 percent). 1

The invention will be better understood from the following detaileddescription of a preferred embodiment thereof, as given by mere way ofnot limiting example and shown in the appended drawings in which:

FIG. 1 is a front view of the machine;

FIG. 2 is a side view thereof;

FIG. 3 is a sectional view taken along line A--A;

FIG. 4 is a sectional view taken along line B-B; and

FIG. 5 is a schematic side view of a modified embodiment.

Referring to FIGS. 14=, the inventive machine is formed of'a framecomprising plates and sections which are welded and bolted to oneanother by conventional techniques, so as to form two sides I and 2interconnected by crosspieces 3 and 4, and a base 5 carrying a speedreducer 6 and which secures the whole assembly to ground by joining thetwo sides at the bottom. Obviously, the frame and base can be made ofcasting, cast iron or steel.

The upper crosspiece 4 carry a trestle 7, at the mid portion of which aloading hopper 8 is provided, this hopper being carried by the frame andcapable of being filled by means of a winch running on a section 10carried by said trestle 7.

As more fully explained below, said frame carries two pairs of heatedrolls 11, 12 and 13, 14 rotating in the direction as shown by the arrowsand symmetrically placed above each other.

Rolls 12 and 14 are fixedly secured by their associated supports l5,tosides 1 and 2, whereas rolls l1 and 13 are movable, or can run throughtheir associated supports 17 on quideways comprising beams 18 formingpart of the structure for each side 1, 2.

Movable rolls ll, 13 can be driven by devices well known in the plasticmaterial calender field, for example comprising four speed reducers 19kinematically connected to the roll supports 17.

As to the top pair of rolls 11 and 12, these rolls operate as highlypressed against each other, roll 12 rotating at a higher speed than rollI], thus exerting a friction on the thermoplastic material being fed bygravity between the rolls from said hopper 8 through its associatedoutlet 16.

This material will adhere to the fastest roll 12, forming a thin sheetor foil which is then removed from the roll surface by a separatingmeans comprising a scraping blade 20.

This blade 20 is mounted (for example fixed) on a shaft 21 rotable ontwo bearings 22 attached to the sides 1 and 2. Two hydraulic orpneumatic jacks 23 act upon this shaft through arms 32 and hinges 32A,said jacks being in turn secured by means of brackets 50 and-hinges 51to the sides 1 and 2. These jacks serve both the purpose of causing saidscraping blade 20 to firmly adhere to the surface of roll 12, and toseparate it therefrom. a

An inclined sheet 24 is also attached on said shaft 21 and, as shown inan operative step in FIG. 4, is for caus ing the scraped plasticmaterial to fall down on an underlying conveyor belt 25.

In order to prevent hot plastic material from tacking on said sheet 24and to facilitate its slipping thereon, it has been contemplated both toprovide the sheet with a suitable vibrating system (such as an electricmotor 26, on the axis of which an eccentric mass 26A is mounted), and totreat the surface contacting the hot material with antiadhesiveproducts, such as Teflon.

The scraped plastic material moves down from the vibrating sheet 24 onthe conveyor belt 25 which is di rectly attached to the sides 1 and 2through two plates 52 acting as side walls. The conveyor belt 25 isdriven by a speed reducer 25A coupled to the axis for one of theconveyor belt rolls and carried by side 2. This conveyor belt isconfined between the two side plates 52 preventing the transportedmaterial from sidewise falling down. The length of the conveyor beltshould be less than that of the underlying roll 14, in order to readlyunload the material at the zone A in FIG. 1, that is at or adjacent anend of said roll. As it will be seen, the conveyor belt 25 is locatedabove the roll 14.

In contrast with the top pair of rolls, the rolls 13 and 14 do notoperate as pressed against each other and can rotate at a same ordifferent speed, according to processing requirements.

On falling down from the conveyor belt 25 on the underlying rolls, thematerial will wrap only one of such rolls (roll 14 in the exampleshown), forming a rotating covering or coating; two borders 27, actingjust as containers, are firmly attached to the sides I and 2 in order toprevent said covering from being transferred at the roll sides.

To promote the natural movement of the plastic material from zone A tothe opposite zone B along roll 14 (FIG. 1) and also to facilitate themixing and homogenization thereof, a pair of parallel rods 28 (FIG. 4)are secured between the machine sides 1 and 2, a slide 29 carrying ablade 29A being slidably mounted thereon. This slide is connected withthe free end of the stem 60 of a double acting cylinder attached to side2. The blade runs parallel to the axis of roll 14 and cuts the plasticcoating on the roll; the movement of this blade from zone A to about themiddle of the roll table is intermittently reciprocating and timed atwill in accordance with the operating requirements.

The thermoplastic material, which also because of the rotating movementof roll 14 will slowly move to the table location B (FIG. 1), hereencounters a pair of per se known parallel knives 30, which are securedat an adjustable spacing on a shaft 62 attached to side 2 and cut a hotcontinuous strip of plastic material. This strip (FIG. 4) is thenwithdrawn by a conveyor belt 31 and carried, for example, to supply acalender.

The four rolls can be heated by means of any system in the field ofcalenders for rubber and plastic materials. For example, as shown inFIG. 1, by means of four connectors 33, protruding from one side of eachroll, the heating fluid is admitted and withdrawn when cooled down. Therolls may be made so as to have a large central chamber (for example, asrolls l3 and 14 FIG. 4), or have a serial of peripheral holes (forexample, as rolls 11 and 12 FIG. 4) intercommunicating and having asmall central chamber, the hot fluid operating therein.

The roll heating system has been briefly described not only in that sucha solution is well known, but also because beating could be provided inmany other ways (by electric resistances or by induction systems, etc.).

Also as to the actuation of the rolls, different systems and criteriacan be used. In the example as shown in FIGS. 1, 2 and 3, two separatedraving units are provided, each of which comprising an electric motor34 either of a constant or variable speed, and through V- belts 35driving a pulley 36 which is keyed on the inlet axis of a reducer 6,therefrom emerging an outlet pin 37 on which a gear 38 is keyed. Inturn, each gear 38 rotably drives two gears 39 keyed on the pins for oneof the top rolls and one of the bottom rolls.

It is as well within the scope of the invention to provide for operatingthe machine also from a single motor, or a plurality of electric motorseither at a fixed or variable speed, or from a single or a plurality ofhydraulic motors both through Vbelts and axial keyings to the reducer.

Referring to FIG. 4, gears 38 on the right will drive rolls l2 and 14,whereas gear 38 on the left drives rolls 1 1 and 13. Substantially, eachdriving unit will drive the two overlying rolls of the two pairs ofrolls.

Rather than by gearings, as above shown, it is also within the scope ofthe invention to drive said rolls 11, 12 13 and 14 by a reducer havingfour outlet pins, universaljoints or the like being keyed thereon androtably driving the machine rolls.

In FIG. 5, showing a modified embodiment of the invention, the samereference numerals are used for designating like or equivalent parts.Moreover, the construction of the machine as shown in this FIG. 5 isidentical to that above described, except for the differences which willbe pointed out in the following description. When considering this, adetailed description of the common parts is deemed not necessary.

Referring to FIG. 5, reference numerals 11 and 12 designate the rolls ofthe top pair, wherein roll 12 rotates at a higher speed. A relativelythin film of plastic material as processed by such a pair of rollsadheres on said roll 12. The plastic material film adhering to roll 12is separated therefrom by a separating means, comprising a scrapingblade 20 carried on a rotable shaft 22, as above described. Thisscraping blade 20 is arranged so that the separated plastic materialdirectly falls down on an underlying conveyor belt 25 at the zonedesignated by A in FIG. 1, that is at the zone where said conveyor beltdoes not extend, directly on the roll 14 of the bottom pair of rolls towhich roll 13 pertains.

As above stated, the separated material partly falls directly down onroll 14 and partly on conveyor belt 25, which carries said material tothe end zone A of said roll, where it is processed by the bottom pair ofrolls 13, 14 and builds up on roll 14 a coating which gradually expandsto the other end of said roll, being removed therefrom by the abovedescribed operations.

What is claimed is:

1. A machine for processing plastic materials, particularly polyvinylchloride, comprising:

a top pair of rotating rolls;

means cooperating with one of said top pair of rolls to separate theplastic material film adhering thereto;

a bottom pair of rolls positioned below said top pair of rolls;

a conveyor belt arranged substantially above one roll of said bottompair of rolls and receiving at least part of the plastic material, saidbottom pair of rolls receiving at an end zone thereof the materialcarried by said conveyor belt.

2. A machine as claimed in claim 1, wherein one roll of at least onepair of said top rolls rotates at a faster speed than the other roll ofthe same pair of rolls, and including a vibrating sheet for at leastpartly unloading the separated material onto said conveyor carrying theseparated material to an end zone of the bottom pair of rolls, by whichpair of rolls the material is processed to a layer adhering to one ofthe rolls and tending to the other end, where it is withdrawn as astrip.

3. A machine as claimed in claim 1, wherein the plastic materialadhering to the roll of the bottom pair of rolls is cut in the directionof the roll axis by an intermittently oscillating blade.

4. A machine as claimed in claim 1, wherein the vibrating plane iscoated with a material for promoting a sliding of the material separatedfrom the top fast roll.

on the underlying conveyor belt.

7. A machine as claimed in claim 6, wherein the position of saidseparating means is selected so that a portion of the separated materialfalls directly down on one roll of the bottom pair of rolls at the zonenot involved by the conveyor belt.

1. A machine for processing plastic materials, particularly polyvinylchloride, comprising: a top pair of rotating rolls; means cooperatingwith one of said top pair of rolls to separate the plastic material filmadhering thereto; a bottom pair of rolls positioned below said top pairof rolls; a conveyor belt arranged substantially above one roll of saidbottom pair of rolls and receiving at least part of the plasticmaterial, said bottom pair of rolls receiving at an end zone thereof thematerial carried by said conveyor belt.
 2. A machine as claimed in claim1, wherein one roll of at least one pair of said top rolls rotates at afaster speed than the other roll of the same pair of rolls, andincluding a vibrating sheet for at least partly unloading the separatedmaterial onto said conveyor carrying the separated material to an endzone of the bottom pair of rolls, by which pair of rolls the material isprocessed to a layer adhering to one of the rolls and tending to theother end, where it is withdrawn as a strip.
 3. A machine as claimed inclaim 1, wherein the plastic material adhering to the roll of the bottompair of rolls is cut in the direction of the roll axis by anintermittently oscillating blade.
 4. A machine as claimed in claim 1,wherein the vibrating plane is coated with a material for promoting asliding of the material separated from the top fast roll.
 5. A machineas claimed in claim 1, including two speed reducing units, each of whichdrives two rolls of a different pair of rolls.
 6. A machine as claimedin claim 1, wherein said separating means are arranged along theperiphery of the fastest roll of the top pair of rolls, so that thematerial being separated from said roll is at least partly brought onthe underlying conveyor belt.
 7. A machine as claimed in claim 6,wherein the position of said separating means is selected so that aportion of the separated material falls directly down on one roll of thebottom pair of rolls at the zone not involved by the conveyor belt.